Apparatus for removing the curl from sheets



Feb. 5, 1963 F. E. MONKS 3,076,492

APPARATUS FOR REMOVING THE cum. FROM SHEETS Filed Oct. :50. 1959 FIG.|

INVEN TOR. Frank E. Monks @WZL J ATTORNEYS atcnt @hicc BfilhAQZ Patented Feb. 5, 1963 3,076,492 APPARATUS FOR REMQVING TIE CUR FR M SHEETS Frank E. Monks, Butler, Pa assignor to Standard Packaging Corporation, New York, N.Y., a corporation of Virginia Filed Oct. 30, 1959, Ser. No. 849,780.

Claims. ((3.1..153-85) This invention relates to apparatus for removing curl from sheets, particularly metal foil and metal foil lamihated sheets.

Metal foil and metal foil; laminated sheets are ductile and possess, dead bendingcharacteristics with the result that they are difficult to handle inprinting presses because of theirtendency to curl, Inprinting presses of the type in which sheets travel around in contact with a rotary cylinder of the press, acurl is imparted to the sheets by the curvature of the cylinder, the curl being greater for cylinders of smaller diameter. A curl isalso imparted to the sheets as they are, stripped from the inked surface of the printing press. The tackinessof the ink tends to cause the sheets t9 cling to. the inked surface beyond the line of tangency between the cylinders of the printing couple with the result that the sheets break away from the cylinder in. a small radius, thereby rolling a curl in the sheets. The tackicr the ink and the more solid the lay, the greater is the tendency of the sheet to curl.

These curled sheets are difficultto handle because when they leave the printing press; they tend to roll up toward the supported leading: edge. In addition, they cannot be properly stacked one on top. of another.

The object of the present invention is to provide means for straightening sheets which have become curled. This object is achieved in the, apparatus of the present invention. by feeding the sheets across and in contact with a reverse bending suction trough which extends transversely of the path along which the sheets are advanced. More specifically, the leading edges of the curled sheets are engaged by grippers; which carry the sheets to and across the suction trough. Preferablythe side of the sheet opposite the printed side is drawn across the trough to avoid smearing the ink on the printed side. The effect of the reverse bending action can be; controlled to remove the curl which has been imparted to the sheet by controlling the suction which is in communication with the trough.

The apparatus of the present invention can be made as a separate unit or it can be incorporated with. various types of sheet handling apparatus.

For a more complete understanding of the present invention, reference may be made to the detailed description which followsandto the accompanying drawing, in which,

FIGURE 1 is a schematic side elevation view illustrating the present invention used in conjunction with a printmg press;

FIGURE 2 is a perspective view of the reverse-bending suction trough, shown in FIGURE 1;

FIGURE 3 is a perspective view of an alternative reverse-bending suction trough; and

FIGURE 4 is a plan view of a sheet moving across a reverse-bending suction trough which extends in a diagonal direction.

Referring to FIGURE I of the drawing, sheets x are fed one at a time between the cylinders 1d and 11 which form a printing couple. The printing press forms no part of the present invention, and it is shown in the drawings primarily to illustrate how the curl is imparted to the sheets. For purposes of this illustration, it is unimportant whether the printing couple is a direct or oifset type printing press. In the printing press shown in FIG- URE 1, the inked impressions are printed on the side 3 of the sheet x by the cylinder 11 and the opposite side b of the sheet backs against the impression cylinder 10. In passing through the printing couple the leading edge of the sheet is engaged by grippers 12 carried by the cylinder 10 and the sheet is carried aroundin contact with the cylinder 10. In a printing press of this type, the curvature of the cylinder 10 will tend to impart a curl to the sheet. The smaller the diameter of the cylinder, the greater will be the tendency of the sheet to curl.

Moreover, the tendency of the printed side of the sheet to adhere to the inked surface of the cylinder 11 will impart a curl in the sheet. The more tacky the ink and the more solid the lay, the greater will be the tendency of the sheet to adhere to the inked surface. The path of travel of a sheet at through the printing couple is shown in a somewhat exaggerated manner in FIGURE 1 to. illustrate the tendency of the sheets. to cling to the tacky inked surface of the cylinder 11 and tobreak away therefrom in a small radius. A sheet printed in this manner, particularly a metal foil or metal laminated sheet, will curl and roll up upon itself as soon as it comes out of contact with the cylinder. 10.

According to the present invention, the sheet is fed from the grippers 12 of the cylinder 10 and delivered to one of the grippers 14 carried by: an endless conveyor chain 15 which travels around the sprockets or pulleys 16 and 16.. in transferring from the grippers 12 to the grippers 14, the leading edge of a sheet is engaged by the grippers 14 before it is released by the grippers 12, so that the leading edge of the sheet is continuously and positively fed from the printing press to the conveyor chain. A sheet transferred to the grippers 14 is carried along the lower span of the conveyor chain across a reverse-bending suction trough, generally designated 17, and ultimately delivered to a delivery stack 18. A curled sheet 3/ not subjected to the action of the reverse-bending suction trough is shown in broken lines in FIGURE 1.

The reverse-bending suction trough is shown more clearly in FIGURE 4, of the drawing. This trough includes a gently curved convex surface 19 on the upstream side of a center slot 2% and a gently curved convex surface 21 on the downstream side of the slot. The slot 2% is in communication with a suction pump or other source of vacuum through a suction conduit 22. The contour of the surfaces 19 and 21 is designed so that the surfaces will not have any substantial bending eifect on the sheet. However, the radius of a curvature a of the sheet as it travels across the slot 29 imparts a reverse-bending action on the sheet which effectively removes the curl therefrom. Diiferent degrees of de-curling action are obtained by regulating the amount of the vacuum which, of course, determines the radius of curvature a by pulling the sheet more or less deeply into the slot Zii. Inasmuch as the printed surface of the sheet is face up, the reverse-bending suction trough 17 will not smear the freshly printed sheet.

A modified form of reverse-bending suction trough 17 is illustrated in FIGURE 3 of the drawing. In this embodiment, rotating perforated rollers 2.5 and 26 are stationed side-by-side, and they are rotatably mounted about the stationary inner sleeves 27 and 23 as the sheets x are drawn across the tops thereof. The inner sleeves 2? and 28 are provided with longitudinal slots 29 and 36, respectively, which slots face upwardly toward the relatively small gap between the perforated rollers 25' and 226. Each of the sleeves is closed at one end and the opposite end is in communication with a suction line so that the perforations of the cylinders 25 and 26, as they pass into registry with the slots 29 and 3d of the sleeves 27 and a 28, respectively, tend to draw the portion of the sheet x passing above the perforated rollers into the gap therebetwecn, thereby forming the radius of curvature (2. Thus, the reverse-bending eii'ect produced is the same as described above with the reverse-bending trough shown in FIGURE 3.

The reverse-bending troughs described above can be arranged at right angles to the path of travel of the sheet or on a diagonal, as shown in 4, to change or control curl in a crossgrain direction.

As explained above, the rotary printing press shown in FIGURE 1 is for illustrative purposes only, and obviously the present invention is usable in coniunction with other types of printing presses, including direct and off-set presses, as well as rotary and flat-bed type presses. Also, while the invention has been described with particular emphasis on tie-curling metal foil and metal laminated sheets, the dc-curling apparatus of the present invention is also useful for removing the curl from paper sheets. For example, in off-set printing presses, the moisture from the plate migrates through the paper stock. This moisture tends to relieve stresses in the paper stock which have been built into the stock for increased strength, and relieving these stresses causes the sheet to curl. This curl, however, can be eliminated by the apparatus described above.

The invention has been shown in preferred forms and by way of example only, and obviously many variations and modifications may be made therein without departing from the spirit of the invention. The invention, therefore, is not to be limited to any specified form or embodiment, except insofar as such limitations are set forth in the claims.

I claim:

1. Apparatus for removing curl from sheets comprising means for gripping the leading edge of a sheet, an open reverse-bending suction trough extending transversely of said sheet and wide enough to insure that a portion of said sheet will be drawn into the trough to impart a reverse curvature thereto while said portion of the sheet is within the trough, and means for producing continuous relative movement between the gripping means and the reverse-bending suction trough to draw the sheet progressively across the trough from the leading end of the sheet to the trailing end thereof.

2. Apparatus as set forth in claim 1 in which the reverse-bending suction trough includes a transverse gap defined between a pair of sheet supporting surfaces, and passage means for bringing said gap into communication with a source of suction to draw a portion of said sheet into the gap.

3. Apparatus as set forth in claim 1 in which the reverse-bending suction trough includes a pair of sheet supporting surfaces defining an elongated slot therebetween, and a conduit establishing communication between said slot and a source of suction.

4. Apparatus as set forth in claim 1 in which the reverse-bending suction trough includes a pair of perforated rollers spaced apart side by side to form a gap therebetween, a conduit within each of said perforated rollers, each of said conduits being in communication with a source of suction and having an elongated slot directed upwardly and toward the gap between the rollers, the suction drawing a portion of the sheet into the gap between the rollers and the sheet imparting rotation to the rollers as it is moved relatively thereto.

5. Apparatus for removing the curl from sheets com prising an open reverse-bending suction trough having a recess therein defined between a pair of sheet supporting surfaces, passage means establishing communication between said recess and a source of suction, means for gripping the leading edge of a curled sheet, and means for imparting continuous translation to said grippers to raw the sheet progressively across the gap of the reversebending suction trough from the leading end of the sheet to the trailing end thereof, the reverse-bending suction trough extending transversely to the path of travel of the sheet.

6. Apparatus for removing the curl from sheets as set forth in claim 5 in which the means for imparting translation to the gripper means includes an endless conveyor which transports the gripping means in an orbital path.

7. Apparatus for removing the curl from sheets as set forth in claim 5 in which the sheet supporting surfaces of the reverse-bending suction trough are convexly curved and in which the recess is an elongated slot between the convexly curved surfaces.

8. Apparatus for removing the curl from sheets as set forth in claim 5 in which the sheet supporting surfaces are perforated rollers and the recess a gap between the perforated rollers, the sheet imparting rotation to the rollers as it is drawn across them.

9 in a sheet handling apparatus, a cylinder around which sheets are fed and which imparts a curvature to the sheets, means defining an open trough extending transversely of the path which the sheets follow when they leave the cylinder, suction producing means communicating with the open trough to draw into the open trough that portion of a sheet above it, and sheet feeding means for advancing a sheet continuously from the cylinder and across the trough defining means.

i In the apparatus set forth in claim 9, a sheet feeding means which includes grippers for engaging the leading edge of the sheet, leaving the trailing edge free.

References Cited in the file of this patent UNITED STATES PATENTS 

1. APPARATUS FOR REMOVING CURL FROM SHEETS COMPRISING MEANS FOR GRIPPING THE LEADING EDGE OF A SHEET, AN OPEN REVERSE-BENDING SUCTION TROUGH EXTENDING TRANSVERSELY OF SAID SHEET AND WIDE ENOUGH TO INSURE THAT A PORTION OF SAID SHEET WILL BE DRAWN INTO THE TROUGH TO IMPART A REVERSE CURVATURE THERETO WHILE SAID PORTION OF THE SHEET IS WITHIN THE TROUGH, AND MEANS FOR PRODUCING CONTINUOUS RELATIVE MOVEMENT BETWEEN THE GRIPPING MEANS AND THE REVERSE-BENDING SUCTION TROUGH TO DRAW THE SHEET PROGRESSIVELY ACROSS THE TROUGH FROM THE LEADING END OF THE SHEET TO THE TRAILING END THEREOF. 